Population increase and environmental deterioration correspond with microlithic innovations in South Asia ca. 35,000 years ago

Abstract

Genetic studies of South Asia's population history have led to postulations of a significant and early population expansion in the subcontinent, dating to sometime in the Late Pleistocene. We evaluate this argument, based on new mtDNA analyses, and find evidence for significant demographic transition in the subcontinent, dating to 35-28 ka. We then examine the paleoenvironmental and, particularly, archaeological records for this time period and note that this putative demographic event coincides with a period of ecological and technological change in South Asia. We document the development of a new diminutive stone blade (microlithic) technology beginning at 35-30 ka, the first time that the precocity of this transition has been recognized across the subcontinent. We argue that the transition to microlithic technology may relate to changes in subsistence practices, as increasingly large and probably fragmented populations exploited resources in contracting favorable ecological zones just before the onset of full glacial conditions. archaeology ͉ environment ͉ genetics ͉ lithic technology

Genetic and archaeological perspectives on the initial modern human colonization of southern Asia

“…The genetic estimates for the earliest arrival predate substantially the first major demographic expansion signatures from mtDNA in South Asia, shown by Bayesian skyline plots (Figs. S2 and S3) to take place 45-50 ka for the minor haplogroup R and 37-43 ka for the major haplogroup M. This reflects both the rapid proliferation of different subclades of the haplogroup M lineage from ∼40 ka onward and a simultaneous increase in the numbers of directly dated microlithic industries in India over the same time range (2). In addition, the regional skyline plots for haplogroup M show progressively more recent founder ages and expansion times moving from the east of India into the interior-possibly reflecting the easier penetration into the eastern Indian interior via the many river valleys (including the Ganges and its tributaries) that flow into the east Indian coast (Figs.…”

“…In demographic terms the most central and critical implication of the pre-Toba model is that there was direct cultural, demographic, and therefore genetic continuity between the hypothetically modern humans who colonized the Indian subcontinent sometime before ∼74 ka and the later populations characterized by the highly distinctive Indian microlithic technologies, known to have occupied effectively all areas of the subcontinent (including Sri Lanka) from at least 35-40 ka onward and continuing for a further 30,000-35,000 y into the ensuing Neolithic period (2,3,5,20,21). As discussed below, this proposal has radical implications for the interpretation of the genetic evidence (Fig.…”

“…2). The second, more recently proposed view, is that there was a much earlier dispersal of modern humans from Africa sometime before 74 ka (and conceivably as early as 120-130 ka), reaching southern Asia before the time of the volcanic "supereruption" of Mount Toba in Sumatra (the largest volcanic eruption of the past 2 million y) at ∼74 ka (1)(2)(3)(4)(5)(6).…”

“…Issues surrounding the initial modern human colonization of the geographically pivotal region of southern Asia have generated intense controversy in the recent genetic and archaeological literature (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13).…”

“…before present (B.P.)] a fragment of ostrich eggshell engraved with a complex "bounded criss-cross" design (2,3,(20)(21)(22) (Figs. 3 and 4).…”